The use of sophisticated placement machines in manufacturing printed circuit or similar cards, boards, panels, etc. is well known. The term printed circuit board (PCB) as used herein refers to any such electronic packaging structure. Typically, reels of tape-mounted circuit components are supplied to the placement machine by multiple feeders. Each feeder holds a reel of components and each feeder assembly provides components at a pick station. A housing carrying a rotatable frame having a plurality of pick/place heads, each pick/place head having a vacuum spindle equipped with a nozzle, may be moved in the X and Y axes in a plane above the PCB being populated. Each vacuum spindle may be moved in the Z-axis (i.e., in and out from an extended to a retracted position). Each nozzle is sized and otherwise configured for use with each different size and style of component to be placed by the machine.
In operation, the housing carrying the rotatable frame is moved to the pick station and the nozzle of one of the pick/place heads is positioned over the tape-mounted component. The nozzle is lowered, via its associated vacuum spindle, to a point where, upon application of vacuum, the component is removed from its backing tape and held tightly against the nozzle orifice. The component is then brought to a vision system where an image of the component is taken and processed. One or more images of the component is captured by the vision system.
Analysis of the image(s) determines whether the component is placeable. Typically, a placeability decision is based on a comparison of the image to predetermined mechanical parameters for each component. If the component is placeable, the rotatable frame is moved to a point over the printed circuit board being assembled and the component deposited on the printed circuit board at a predetermined location. If a component is non-placeable, it is rejected into a reject station. With multi-pick/place head machines, the need to reject components efficiently to improve cycle rate has become more critical. The mechanical parameters used for comparison may include, but are not limited to, lead length, lead width, lead spacing, component size, the number of leads, etc.
It is also known in the art to use a gripping mechanism that may be extended and retracted in place of the vacuum spindle and nozzle.
In the past, when the nozzle of a particular pick/place head carried a component deemed non-placeable, the entire housing and rotatable frame had to be moved in the X-Y plane to a designated reject station to release the component. This reject station may be a dump bucket, a reject feeder, or a matrix tray. Needless to say, as the entire multi-head rotatable frame needed to move, all other pick/place heads thereupon were prevented from picking and placing components during the trip to the reject station. This resulted in lower placement machine throughput because of this motion.